Jeep Check Engine Light Stays On Causes & Solutions

Does the Check Engine Light appear on your Jeep? Learn the cause of the check engine light coming on and possible solutions for the warning light to go out using an OBD-II scanner.

The Jeep Check Engine Light (CEL) illuminates when the Jeep On-Board Diagnostics (OBD) system detects a problem with the engine, transmission, or evaporative system. This article covers the common problems that cause your Jeep’s check engine light to come on, the symptoms, and how to read the trouble codes yourself with an OBD-II scanner.


Common symptoms you notice when your Jeep check engine light comes on:

Check engine light always on
Engine runs rough
Engine misfire present
Lack of engine power
poor throttle response
engine noise
exhaust smoke
excessive heating

Jeep Check Engine Light Causes & Solutions

Did you see the check engine light on your Jeep and wonder what the jeep check engine light means? If so, worry no more because you are in the right place.

The jeep check engine light is an indicator that is commonly misunderstood. The check engine light is an important aspect of the jeep’s on-board diagnostic system, displayed as “check engine” or an engine symbol.

Sometimes, it can be seen as a union of both. It glows in colors like red, and can sometimes be amber.

As you read more in this article, you’ll learn everything you need to know about your jeep’s check engine light, including what it means, what causes it, and how to reset your jeep’s check engine light.

What does the check engine light mean on a Jeep?

When your Jeep’s check engine light comes on, the on-board diagnostics system has detected a problem with the engine, the emissions system, and in some cases, even the transmission. The most common problems that cause Jeep check engine lights to come on are worn spark plugs, faulty oxygen sensors, or loose gas caps.

In a situation where Jeep’s Electronic Control Module (ECM), known as the vehicle’s computer, detects a problem it cannot resolve, a system is programmed to automatically turn on the check engine light.

This could be a symbol or diagram for an engine; it could also be a diagram with a “check” displayed in a yellowish color on the screen.

The ECM stores a trouble code or engine code when the jeep’s check engine light comes on. This code represents the problem with the engine, be it a faulty engine part or sensor.

An electronic scanner can then be used to read this code for a clear interpretation. You can get cheap code readers if you want to read the code yourself.

However, you will need a professional who understands these codes for a proper diagnosis and possible lasting solution.

What Causes the Check Engine Light to Come On in a Jeep

Anytime the jeep check engine light is on, it may be that the gas cap needs to be adjusted or replaced.

Similarly, the light can also come on due to a major complication which can lead to considerable engine detriment and will require a high repair cost.

The jeep’s check engine light might come on or flash. This is based on the type of engine frame.

When the jeep check engine light comes on and is constant, it shows that the problem is not that serious; however, when the light illuminates as a dazzling light or flashes, it indicates that the vehicle’s engine is in a critical condition and should be serviced immediately.

The following are various issues that could trigger your jeep’s check engine light

1. Damaged spark plugs or spark plug wires

A spark plug ignites the fuel or air inside a vehicle’s combustion chamber. This ignition drives the connecting rods, allowing the engine to run. The spark plug wires take the spark from the ignition coil and carry it to the spark plug.

When these spark plug wires or the spark plug fail, it causes a reduction in power and a depreciation in performance. The engine finds it difficult to start and stops working in the worst case.

Old spark plug wires and spark plugs could destroy the oxygen sensor and ignition coil, which are expensive to repair and lead to a clogged catalytic converter. This can activate the jeep check engine light on a jeep.

Reset Jeep Check Engine Light follow this steps

The first step in the troubleshooting process is to read the fault codes from the Engine Control Unit. This is a simple procedure that you can do yourself with an OBD-II scanner

1. Locate the OBD-II port under the dash and plug in your scanner. The jeep obd ii port is used to diagnose check engine light.

2. Turn on the ignition but do not start the vehicle.

3. turn on the ignition Power on the scanner and allow it to communicate with the vehicle. Diagnose read reset jeep check engine light

4. Select Read Codes or Read Fault Codes depending on the scanner.

5. Fix the problems that arose when you read the codes. Go back to the main menu and select Clear Fault Codes. If the issues were not addressed, the check engine light would return.

Write down the codes that appear on the screen of your OBD-II scanner. For example, a fault code may display as P0301 or P0300. Please investigate those codes to gain a better understanding of the problem

2. Problem with aftermarket replacement parts.

Some jeep aftermarket parts can cause major problems when not fitted correctly. They can damage the batteries and cause the jeep’s check engine light to come on or prevent the vehicle from starting.

3. A vacuum leak

Every Jeep has a vacuum system that serves a multitude of purposes. The vacuum system helps reduce harmful emissions by absorbing excess gasoline vapors as they evaporate through the engine.

A vacuum leak can cause a random increase in RPM when driving or idling. Vacuum hoses, over time, can become crisp and crack, especially when in contact with intense high temperatures, and this can cause your jeep’s check engine light to come on

4. Loose gas cap

jeep check engine light
The jeep’s check engine light will often illuminate due to a loose, improperly attached, or damaged gas cap. The gas cap performs numerous functions. Avoid smoking if the vehicle is not running; it shuts off the fuel system and also helps maintain strength in the tank where the fuel is.

However, when the gas cap is loose or damaged, the gas in the tank evaporates, requiring you to visit a gas station frequently.

Fortunately, changing the gas cap to solve this problem is inexpensive and you can get a new gas cap for your vehicle at many auto parts stores. In a situation where the jeep’s check engine light comes on before you fill the gas tank, examine the gas cap to make sure it’s not loose.

5. Low or discharged battery

Another reason the jeep check engine light comes on is a low or dead vehicle battery. Batteries in vehicles are essential because, in their absence, the car will not respond or start to work; you can’t even listen to music or even charge your mobile devices.

Compared to years ago, the durability of a vehicle’s batteries is greater. The battery takes a long time to run out and does not need to be preserved. Depending on the make and model of your vehicle, the cost of the battery will vary.

6. Faulty O2 Sensor

A faulty O2 sensor in a jeep can cause the jeep’s check engine light to come on. A damaged oxygen sensor does not affect the number of miles on a jeep; instead, the spark plug and catalytic converter will be affected.

The O2 sensor helps your vehicle’s on-board computer regulate the air and fuel mixture going into your engine’s cylinders.

Also read: How to remove the O2 sensor without a plug (step by step)

7. Damaged catalytic converter

A bad catalytic converter can cause your jeep’s check engine light to come on.

Catalytic converters are an important component of the Jeep exhaust system. The catalytic converter aims to convert the CO, produced through the oxidation process, into CO2. The most common cause of a malfunctioning catalytic converter is improper maintenance.

A damaged catalytic converter will fail the emissions test. This represents a deficiency in the performance of the engine, which, in turn, will increase the financial cost of your car, such as the cost of fuel.

8. Faulty Maf Sensor (Mass Air Flow Sensor)

The MAF sensor regulates the amount of fuel that will actually start the engine. This is accomplished by measuring how much air is drawn into the engine.

The MAF sensor helps adapt to disturbances such as altitude as it is a segment of the engine management system. If your Jeep’s accelerator pedal suddenly changes location or you have trouble starting it, it could indicate that the MAF is not in good condition, which will cause your Jeep’s check engine light to come on.

What activates the check engine light on a Jeep?

The most common causes that activate the check engine lights include:

Oxygen sensor
ignition coils
catalytic converter
Loose gas cap

The next section covers some other issues that trigger the Jeep’s check engine light.

Thermostat: Stuck or non-opening engine thermostats are a fairly common problem on Jeep vehicles. In addition to a check engine light, you may also experience engine overheating or high fuel consumption, depending on the failure mode. In both cases, the thermostat must be replaced without delay. Code: P0128 – thermostat is not working properly

EGR Valve – On Jeep engines, the EGR related problem is usually caused by a stuck EGR valve. If it gets stuck, this can cause rough running, misfires, and stalling. In most cases, carbon buildup inside the valve prevents proper operation. If it’s not too serious, it can be cleaned with an EGR cleaner spray. Code: P0404 – EGR Performance

Catalytic Conversion: Higher mileage Jeeps are likely to have issues with their emission control systems. In most cases this is due to a worn catalytic converter or dirty O2 sensors. Identify the root of the problem before replacing expensive parts. Codes: P0420 and P0430 – Catalyst Efficiency Below Threshold

EVAP Leak – A check engine light with a strong gas odor could indicate a leak within the EVAP system. The purge solenoid is the first thing to check for leaks and fuel vent lines. Some models have a leak detection pump, which can go bad. Codes: P0456 – small evaporative leaks, P1494 – Faulty leak detection pump or evaporative leak.

Transmission: Gearbox-related issues can also trigger the check engine light. You may experience rough shifting or get stuck in second gear, which is called limp mode. In most cases, replacing the transmission valve body fixes the problem. Fault Code: P0740

Throttle Body: Newer Jeeps with 4-cylinder engines are prone to electronic throttle body issues. This will cause a rough idle, loss of power, and poor throttle response. In some cases, it can even trigger an extremely limited emergency boot mode. Replacing the throttle body is the only way to solve the problem. Codes: P2112 and P2112 – Throttle Actuator Control System – Stuck Open

Jeep Check Engine Light Flashing

If you notice the jeep’s check engine light flashing, it means that a fault has been detected that requires immediate attention. Also, flashing jeep check engine light means that the problem is very likely to damage the engine; this could cause a big problem for the car if not taken care of right away.

Flashing of your Jeep check engine light could indicate a serious engine misfire, allowing fuel that is not burning or burning properly to pass through the exhaust.

This can cause the temperature of the catalytic converter to rise rapidly, leading to significant damage and a high repair cost.

Some car owners may ask if a bad spark plug could cause the check engine light to flash on a jeep.

Yes, this could happen because an engine could misfire when the spark plug is old, worn, or faulty.


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